“…6 and are characterized by a doublet centered at g = 2.023 ± 0.002 ascribed to phosphorous oxygen hole center (POHC). The term POHC designates the defect responsible for a well-known ESR spectrum in irradiated phosphate glasses characterized by an approximately g tensor with g~2.009 ± 0.002 and a small, nearly isotropic 31 P hyperfine interaction (~40 G) [2,19]. The g value of the doublet is larger than that of the free spin, consistent with the nature of the hole center.…”